The external keratin tissue, which represents the protective covering of the human body, encompassing hair, skin, and nails. Keratinous tissues are normally acidic, having isoelectric points on the acidic side of the pH scale. Acidity causes the amino acid cystine, which has a disulfide bond to cleave with concomitant lose in the tensile strength of hair.
A well know method for improving the cosmetic feel and appearance of hair is to treat it with compositions contain polypeptides obtained from partial hydrolysis of collagen, wheat protein, or wheat starch and the like. U.S. Pat. Nos. 3,683,939; 4,186,188, and 4,793,992 teach this prior art.
High molecular weight anionic polymers, like polystyrene sulfonate are also know in the prior art as cosmetic ingredients. National Starch and Chemical Company describes the use of such a product known as Flexan(copyright) 130.
It is an ionic polymer with excellent electrical conductivity. Films made from this polymer are hard, tough, but water-soluble.
It has now been unexpectedly found that certain cosmetic preparations for treatment of keratinous tissue containing polymeric aspartic acid and polystyrene sulfonate have unique properties for the treatment of hair. Specifically these cosmetic preparations comprise aqueous solutions having a pH range of about 5 to about 9.
The molecular weight of polyaspartic acid can range from about 2,000 to about 50,000. The sodium salt of polystyrene sulfonate should have a molecular weight range of about 15,000 to about 500,000.
Keratinous tissue treated with cosmetic preparations embodying features of this invention exhibit cosmetic characteristics including excellent anti-static properties, improved manageability, body and sheen, improved curl retention and does not impart stickiness, greasiness or build-up problems.
This invention teaches cosmetic compositions, which are useful for treating keratinous, tissue, particularly hair. For the most part these are aqueous solutions of polyamino acids and high molecular weight anionic polymers having acidic functionality""s, or salts thereof.
These unique compositions can be altered through the use of a variety of additives. Alcohols, silicones, water-soluble thickeners, plasticizers, surfactants, humectants, lubricants, proteins, and other modifiers can be added to achieve a desired effect. Anyone skilled in the art of cosmetic formulations can decipher which ingredients are required for a particularly property. In general, none of these additives, at low concentrations will detract from the desired properties of the novel combination obtained by the teachings of this invention.
There are several variables which have been found to be important to achieve optimum results, which consist of excellent anti-static properties, even at very low humidity, improved manageability, body and sheen, curl retention, no stickiness or greasiness or build-up problems.
The combination of these two polymeric materials in aqueous solution can tolerate a wide range of pH from about 5 to greater than 9. A preferred range would be from about 7 to about 9.
The concentration of the two active polymers is also important. If too little  less than 0.5 wt. % is used the desired effects are minimized, while higher concentrations  greater than 6 wt. % an undesirable stiffness imparted to the hair fibers will result. The preferred range of concentration for each ingredient is from about 0.5 to about 3.5 wt. %.
A third variable is molecular weight. The polyamino acid is the lower molecular weight polymer. It can range from about 1,000 to about 50,000. The preferred range is from about 2,000 to about 20,000. In contrast and unexpectedly, the molecular weight of the acidic anionic polymer can range from 25,000 to about 500,000 with a preferred range of about 50,000 to about 200,000.
What is quite novel and unexpected with the cosmetic compositions of this invention is the fact that our polymeric compositions have a significant anionic nature even at a pH of 6 (Determined by FTIR). This is particularly true when the polyamino acid is polyaspartic acid. There are several forms of polyaspartic acids, generally known as alpha, beta or gamma. All of these structural modifications are acceptable for the teachings of this invention. A particularly desirable polyaspartic acid is available commercially. It is called Donlar A-3C (Donlar Corporation, Bedford Park, Ill.). It has a molecular weight of 3,000.
A preferred strong anionic polymeric material which functions within the scope of this invention is available commercially. It is known as Flexan(copyright) 130 (National Starch and Chemical, Bridgewater, N.J.). It""s molecular weight is approximately 130,000.